Zhibing Li

Government of the People's Republic of China, Peping, Beijing, China

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Publications (48)64.63 Total impact

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    ABSTRACT: We investigate continuous-time quantum walks of two indistinguishable particles [bosons, fermions or hard-core bosons (HCBs)] in one-dimensional lattices with nearest-neighbor interactions. The results for two HCBs are well consistent with the recent experimental observation of two-magnon dynamics [Nature 502, 76 (2013)]. The two interacting particles can undergo independent- and/or co-walking depending on both quantum statistics and interaction strength. Two strongly interacting particles may form a bound state and then co-walk like a single composite particle with statistics-dependent walk speed. Analytical solutions for the scattering and bound states, which appear in the two-particle quantum walks, are obtained by solving the eigenvalue problem in the two-particle Hilbert space. In the context of degenerate perturbation theory, an effective single-particle model for the quantum co-walking is analytically derived and the walk seep of bosons is found to be exactly three times of the ones of fermions/HCBs. Our result paves the way for experimentally exploring quantum statistics via two-particle quantum walks.
    09/2014;
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    ABSTRACT: We investigate continuous-time quantum walks of two indistinguishable particles (bosons, fermions or hard-core bosons) in one-dimensional lattices with nearest-neighbour interactions. The two interacting particles can undergo independent- and/or co-walking dependent on both quantum statistics and interaction strength. We find that two strongly interacting particles may form a bound state and then co-walk like a single composite particle with statistics-dependent propagation speed. Such an effective single-particle picture of co-walking is analytically derived in the context of degenerate perturbation and the analytical results are well consistent with direct numerical simulation. In addition to implementing universal quantum computation and observing bound states, two-particle quantum walks offer a novel route to detecting quantum statistics. Our theoretical results can be examined in experiments of light propagations in two-dimensional waveguide arrays or spin-impurity dynamics of ultracold atoms in one-dimensional optical lattices.
    02/2014;
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    ABSTRACT: Coherent emission of electron from graphene in both electric and magnetic fields is studied. We obtain the emission wave function analytically. The emission current density is calculated. The structure of Landau levels is recognizable in the emission image. The emission pattern depends on the phase difference of two sub-lattices. We find that the pattern changes obviously with the gate voltage on the edge. It provides a way to manipulate the emission pattern.
    Journal of Applied Physics 01/2014; 115(5):053701-053701-4. · 2.21 Impact Factor
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    ABSTRACT: The deformation and disintegration of a graphene nanoribbon under external electrostatic fields are investigated by first principle quantum mechanical calculations to establish its stability range. The zigzag edges terminated by various functional groups are considered. By analyzing the phonon spectrum, the critical fracture field for each edge structure is obtained. It is found that different terminal groups on the zigzag graphene nanoribbons lead to different fracture patterns at different fracture fields.
    Physical chemistry chemical physics : PCCP. 11/2013;
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    ABSTRACT: We apply non-equilibrium thermodynamics to describe the adsorption and desorption of molecular hydrogen on graphene. Lateral interactions, precursor states in both adsorption and desorption, and limited dimer conversion are important to explain semi-quantitatively the main features of temperature-programmed desorption spectra. All energy and vibrational parameters are taken from density functional calculations. Deficiencies in previous attempts are discussed. We also point out the need for a multi-dimensional dynamic theory.
    Surface Science 11/2013; · 1.84 Impact Factor
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    ABSTRACT: We obtain the wave function of field emission from graphene in magnetic field. The emission image reveals structure of the Landau levels and depends on the phase difference between two sub-lattices. The emission pattern is sensitive to the edge potential shift, so a gate voltage can manipulate that.
    02/2013;
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    ABSTRACT: Graphene superlattices formed by adsorbing oxygen lines on graphene are studied using spin-polarized density functional theory calculations. It is found that separating zigzag chains (armchair dimer lines) with one oxygen adsorbate on each periodic segment of the chain (line) are sufficient to divide the graphene sheet into series of graphene nanoribbons. The energy band gap of the graphene with armchair (zigzag) oxidation lines (chains) is modulated with line (chain) separation as the width modulation of the freestanding graphene ribbon. The magnetic properties of superlattices with different oxidized line width for both zigzag and armchair oxidized lines are also investigated. Magnetism is found in oxygen-patterned graphene superlattice with zigzag interface and is enhanced with the increasing width of separating oxidation chains.
    Journal of Applied Physics 12/2012; 112(11). · 2.21 Impact Factor
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    Weiliang Wang, Zhibing Li
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    ABSTRACT: It is common practice to extract field enhancement factor from the slope of FN plot. Many experimentalists working on field electron emission had reported multi-(linear segment) FN plots, which can be divided into several (usually two) linear segments. Then multi-(field enhancement factor) were extracted from the FN plot. They claimed that the field enhancement factor increases with applied field if the FN plot bends downward (vice versus if the FN plot bends upward). We show that this is contrary to fact.
    11/2012;
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    Weiliang Wang, Zhibing Li
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    ABSTRACT: An extraordinary low vacuum barrier height of 2.30 eV has been found on the zigzag-edge of graphene terminated with the secondary amine via the ab initio calculation. This edge structure has a flat band of edge states attached to the gamma point where the transversal kinetic energy is vanishing. We show that the field electron emission is dominated by the flat band. The edge states pin the Fermi level to a constant, leading to an extremely narrow emission energy width. The graphene with such edge is a promising line field electron emitter that can produce highly coherent emission current.
    Applied Physics A 09/2012; 109(2). · 1.69 Impact Factor
  • Chunshan He, Zhibing Li, Weiliang Wang
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    ABSTRACT: The work functions of (001) and (00-1) surfaces of B4C are investigated with density functional theory and symmetry slab model. These two surfaces are found to be almost nonpolarized and their work functions are 5.15 eV and 5.46 eV, respectively.
    Surface Review and Letters 08/2012; 19(4):50040-. · 0.28 Impact Factor
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    ABSTRACT: We report the effect of carbon–oxygen atomic ratio (C/O ratio) on the field emission properties of the chemically reduced few-layer graphite oxide (GO). The field emission properties are found to be a non-monotonic function of the C/O ratio in a wide range of 2.06–14.80. Samples with C/O ratio of 6.98 show the lowest turn-on (1.80 MV/m), threshold fields (5.15 MV/m) and much higher current density (44.08 mA/cm2 at 9.00 MV/m). Long-time (10 h) current stability test of the GO at a high current density (∼13 mA/cm2) resulted in the reduction of the GO. The samples with field emission induced reduction show the same non-monotonic effect of the C/O ratio on the field emission properties as that of the chemically reduced GOs. The average current fluctuation of the GO is higher than that of the reduced GO, which is due to the oxygen desorption during the electron emission. The effect of the carbon–oxygen bonds on the surface potential barrier of the reduced GO edges is proposed in detail for interpreting the experimental observations.
    Carbon. 06/2012; 50(7):2657–2665.
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    ABSTRACT: We investigated the stability of reduced graphene oxide for oxygen density ranging from 6.25% to 50% with the density functional theory and found the most, the second most, and the third most stable oxygen configurations. The effect of relaxation of lattice on the electronic properties is found to be negligible for low O coverage and crucial for higher O coverage, respectively. The densities of states and the band gaps were calculated. The bandgap is found to be a non-monotonic function of oxygen density, with minima at O/C = 11.1% and 25%.
    Journal of Applied Physics 03/2012; 111(5). · 2.21 Impact Factor
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    ABSTRACT: We report the preparation and field emission characterization of the chemically-reduced graphene oxide (RGO) thin film and the integration of the RGO films with the MOSFET for realizing the actively-controlled on the emission current. Physical mechanisms are proposed for interpreting the effect of the carbon-oxygen bonds on the field emission properties.
    Vacuum Electronics Conference (IVEC), 2012 IEEE Thirteenth International; 01/2012
  • Weiliang Wang, Junwen Shao, Zhibing Li
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    ABSTRACT: We investigated the vacuum potential barriers of various graphene edges. It is found that the exchange-correlation potential correction is significant to the edge structures with electronegativity higher than carbon. The correction leads to the local work function decreased by more than 1 eV for the O terminated edge. An extraordinary low vacuum barrier height of 2.0 eV has been found on the zigzag-edge of graphene terminated with the secondary amine via the ab initio calculation. This edge structure has a flat band of edge states attached to the gamma point where the transversal kinetic energy is vanishing. We show that the field electron emission is dominated by the flat band. The edge states pin the Fermi level to a constant, leading to an extremely narrow emission energy width. The graphene with such edge is a promising line field electron emitter that can produce highly coherent emission current.
    Vacuum Nanoelectronics Conference (IVNC), 2012 25th International; 01/2012
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    Weiliang Wang, Junwen Shao, Zhibing Li
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    ABSTRACT: We investigated the vacuum potential barriers of various graphene edges terminated with hydrogen, oxygen, hydroxyl group and ether group respectively. It is found that the exchange-correlation potential correction is significant to the edge structures with electronegativity higher than carbon. The correction leads to the local work function decreased by more than 1. eV for the O terminated edge, while the local work function of H and OH terminated edges remain unchanged.
    Chemical Physics Letters 12/2011; 522. · 2.15 Impact Factor
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    Xizhou Qin, Weiliang Wang, Zhibing Li
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    ABSTRACT: The cold field electron emission from metallic nanowall array is investigated theoretically. Via conformal mapping method, analytic formulas of tunneling barrier, edge field enhancement factor, transmission coefficient, and area emission current density are derived in the semi-classical approximation. The influence of field enhancement effects and screening effects on cold field emission are discussed and the optimal spacing distance between nanowalls for the largest emission current density is found to be a linear function of the height of nanowalls and depends on the applied field.
    11/2011;
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    ABSTRACT: Electrons in the mono-layer atomic sheet of graphene have a long coherence length of the order of micrometers. We will show that this coherence is transmitted into the vacuum via electric field assisted electron emission from the graphene edge. The emission current density is given analytically. The parity of the carbon pi-electrons leads to an image whose center is dark as a result of interference. A dragonfly pattern with a dark body perpendicular to the edge is predicted for the armchair edge whose emission current density is vanishing with the mixing angle of the pseudo-spin. The interference pattern may be observed up to temperatures of thousand Kelvin as evidence of coherent field emission. Moreover, this phenomenon leads to a novel coherent electron line source that can produce interference patterns of extended objects with linear sizes comparable to the length of the graphene edge.
    Physical review. B, Condensed matter 10/2011; · 3.77 Impact Factor
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    Xizhou Qin, Weiliang Wang, Zhibing Li
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    ABSTRACT: The electric field around a nanowall that is vertically mounted on a planar cathode is studied. The system is designed as a cold field electron emitter or an electron tunneling line scanner. Exact expressions for the electric potential and the edge field enhancement factor are obtained for arbitrary cathode-anode distances. It is found that the finite distance correction is significant for the cathode-anode distances less than twice the height of the nanowall. The angle-dependent transmission probability implies that the forward emission is dominant.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 06/2011; · 1.36 Impact Factor
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    ABSTRACT: The field electron emission current from graphene is calculated analytically on a semiclassical model. The unique electronic energy band structure of graphene and the field penetration in the edge from which electrons emit have been taken into account. The relation between the effective vacuum barrier height and the applied field is obtained. The calculated slope of the Fowler-Nordheim plot of the current-field characteristic is in agreement with existing experiments.
    Journal of Applied Physics 05/2011; · 2.21 Impact Factor
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    Weiliang Wang, Zhibing Li
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    ABSTRACT: We calculated row resolved density of states, charge distribution and work function of graphene's zigzag and armchair edge (either clean or terminated alternatively with H, O or OH group). The zigzag edge saturated via OH group has the lowest work function of 3.76 eV, while the zigzag edge terminated via O has the highest work function of 7.74 eV. The angle-dependent potential barrier on the edge is fitted to a multi-pole model and is explained by the charge distribution.
    Journal of Applied Physics 04/2011; 109. · 2.21 Impact Factor

Publication Stats

150 Citations
64.63 Total Impact Points

Institutions

  • 2014
    • Government of the People's Republic of China
      Peping, Beijing, China
  • 2005–2011
    • Sun Yat-Sen University
      • • State Key Laboratory of Optoelectronic Materials and Technologies
      • • School of Physics and Engineering (SPE)
      Guangzhou, Guangdong Sheng, China
  • 2004
    • The University of Hong Kong
      • Department of Chemistry
      Hong Kong, Hong Kong
  • 2003–2004
    • Zhongshan University
      Shengcheng, Guangdong, China